Types of Dental Implants

Dental implant supported prosthesis have become an important therapy for patients with some and all missing teeth. There are three main designs of dental implants: subperiosteal implants, transosseous implants and endosseous.  Let’s discuss the difference between them.

Subperiosteal Dental Implants

These implants are individually designed cast-metal frames made from an impression and master cast of the anatomical site where the implant will be placed.  Metal posts project from the implant frame to penetrate the oral mucosa and enter the mouth.  Support and retention of an implant prosthesis are provided by these posts.

The subperiosteal dental implant is cast in surgical vitallium, and is without special surface coating or preparations.  The implant frame rests on bone for support, and may or may not be fixed to the bone by screws.

Both short and long edentulous spans in the maxilla and mandible have been restored by this implant.  However, it has been primarily used for the lower jaw of a patient without any lower teeth.

Transosseous Dental implants

These implants pass through bone.  The transosseous dental implant consists of a flat bone plate fitted to the lower border of the mandible.  Projecting from the bone plate are a number of posts.  Some posts insert into the bone for retention, while other posts pass through the bone to penetrate the oral mucosa.  Prosthetic attachments that fit the intraoral posts provide the means of prosthesis retention.

Transosseous design variations relate to the number of posts on the bony plate for retention, and the number that penetrate the oral cavity for prosthesis support.  There are normally two or four posts for the prosthesis retention, depending on the specific patient’s prosthodontic needs.

Transosseous dental implants are machined from commercially pure titanium, a titanium alloy, or a gold alloy, unlike subperiosteal dental implants, which are cast.  The surfaces of the posts are threaded, and special surface coatings or preparations are not customary.

Endosseous Dental Implant

Endosseous implants are the most common dental implants used today.

Endosseous dental implants are positioned within the jawbone and gain support from bone by osseointegration.  The dental implant designs are varied, yet generally conform to the shape of a natural root.  Other implant forms are screws.

The endosseous implant is machined from commercially pure titanium or a titanium alloy, and is cleaned, sterilized, and packaged in a sterile container ready for use.  The endosseous dental implant surface may be coated or sprayed to create a textured surface to potentially enhance osseointegration.

Generally, endosseous dental implants have an interosseous component surgically placed in the patients maxilla or mandible, and called simply the implant.  This provides retention for the entire dental implant structure.  A cover screw may be used during initial healing.

The implant abutment cylinder, usually referred to simply as the abutment, is joined to the implant fixture and penetrates the mucosa, entering the oral environment as the transmucosal component of the implant framework.  The abutment is attached to the implant with the abutment screw.  The accurate orientation of these two components at their interface varies for each endosseous implant.  In certain endosseous implants, the implant and abutment are designed as a single unit, eliminating the need for an abutment screw.  These two components in combination represent the tooth root analog.

The third component in endosseous implant is similar to a post and core in conventional prosthodontics, which may be a single unit or two separate parts.  Located in the center of the abutment screw is a threaded opening that will accommodate the screw used to join the core to the abutment.  For some single tooth implants, the core is incorporated into a wax pattern that is cast to form a framework on which porcelain is fused or artificial teeth processed to produce the implant prosthesis.  The finished dental crown is attached to the abutment by a gold screw.  For some endosseous implants, the core is made from dense sintered aluminum oxide and offers optimal esthetics when combined with an outer layer of porcelain.  In still other situations, the abutment is shaped to receive a replacement crown made and cemented to the abutment in a conventional manner.

Regardless of design, endosseous implants are the basic tooth root analog units in implant prosthodontic protocols, and are by far the most frequently used implants for oral rehabilitation.

The diagnostic mounting can help initiate design of the dental implant prosthesis.  The definitive prosthesis will differ depending on the location and dimensions of the space that needs teeth replaced and on the success of  dental implant placement. Single-tooth replacement, multiple tooth spans in partially edentulous jaws, and the totally edentulous arch are the most frequent clinical situations treated with implants.  The presence or absence of specific factors in each of these situations, as observed clinically and/or determined from the diagnostic mounting, contribute to determining the best implant design.